Computational thermodynamic model for the Mg-Al-Y system

The ternary Mg-Al-Y system was thermodynamically modeled based on the optimization of the binary subsystems Mg-Al, Mg-Y, and Al-Y using the CALPHAD approach. Mg-Al data was taken from the COST507 database, whereas the other two binary systems were reoptimized in this work. The liquid phase was described by a Redlich-Kister polynomial model, and the intermediate solid solutions were described by it sublattice model. Ternary interaction parameters were introduced to enable the best representation of the experimental data while considering the occurrence of the ternary compound Al4MgY. The constructed database is used to calculate and predict thermodynamic properties, binary phase diagrams of Al-Y and Mg-Y, and liquidus projections of the ternary Mg-Al-Y. The calculated phase diagrams and the thermodynamic properties are in good agreement with the corresponding experimental data from the literature. Sixteen ternary four-phase-equilibria invariant points were predicted in the Mg-Al-Y system: seven ternary eutectic points, eight ternary quasi peritectic points, and one ternary peritectic point. Further, fifteen three-phase-equilibria invariant points were determined: eight saddle points and seven binary eutectic points.